A growing evidence base has demonstrated the value of Forest School as an outdoor learning approach which supports a range of benefits including improved physical, social and mental wellbeing, increased confidence and self‐esteem and the development of problem‐solving skills. However, critics of Forest School have argued that a lack of theoretical coherence and detail risks the misinterpretation of Forest School and its pedagogy by both practitioners and researchers. This paper responds to these concerns, establishing a comprehensive and detailed theoretical framework for Forest School. Through a thorough examination of evidence supporting Forest School delivery, we examine the theoretical keystones of this pedagogical approach to inform an interdisciplinary theoretical understanding of Forest School. We argue that Forest School is a particular socially constructed approach to outdoor education, which is informed by social constructivist experiential learning theory. This is driven by two core components. First, play‐pedagogy, which includes the opportunity to experience risk and be creative. Next, biophilic interaction, which examines the human innate desire to be in nature. This is informed by the cultural origins of Forest School development as underpinned by Nordic notions of friluftsliv and by theories of place attachment. Taken together, this theoretical framework considers the breadth of knowledge that underpins Forest School and recognises its growing evidence base, which positions it as a rich and valuable pedagogical approach.